Mechanical compressor unloader



Feb. 25, 1964 o. H. KAMINKY 3,122,349

MECHANICAL COMPRESSOR UNLOADER Filed July 26, 1961 United States Patent tlice alessia Patented Feb. 25, 1964 3,122,349 MECHANICAL CMPRESSR UNLGADER Oscar H. Kaminky, Goshen, Ind., assigner to Penn Controls, Inc., a corporation of Indiana Filed July 26, 1961, Ser. No. 126,939 5 Claims. (Cl. 251-58) The present invention relates to a mechanical compressor unloader for relieving the air pressure in the output line of a compressor after the compressor has stopped in order that the compressor will be started under a noload condition.

Normally an air compressor has diiculty in starting up against a high air pressure in its output line. Therefore many control devices have been developed to unload this pressure from the output line during the time the Compressor is stopped and again close the valving means which are utilized to unload the line before the compressor starts again. U.S. Patent 3,046,368, issued to this inventor on July 24, 1962, discloses a new and improved compressor unloader which senses the pressure of a volume of air in a container being supplied by a compressor and opens a venting valve to unload the compressor while the pressure of the volume of air is decreasing7 and to close the venting valve again before the pressure in the container drops to the point at which the compressor is placed into operation. The switching means to control the operation of the compressor may be included in the control device for the venting of the compressor line. To accomplish this action a one-way magnetic clutch was illustrated in an embodiment of that invention. A magnetic device is more diliicult to adjust than a purely mechanical one for unskilled labor which may be called upon to install compressors and `controls therefor. Thus the present invention accomplishes the result of my copending application with the use of only mechanical elements.

It is therefore an object of the present invention to provide a completely mechanical compressor unloader which opens a venting valve during the decrease of pressure in a container and closes the venting valve before the energizing of an associated compressor.

A further object is to provide a new and improved compressor unloader.

Another object is to provide a pivoted element mounted on an arm connected to a venting valve, which engages and then disengages another arm only when that arm is moving in agiven direction.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic diagram of an air compressor system into which an embodiment of the present invention may be incorporated;

FIGURE 2 is a side sectional view of an embodiment of the present invention taken along the line 2 2 in FIGURE 3; and

FIGURE 3 is an end elevational view with a cover removed and with a valve portion shown in section of the embodiment of the invention illustrated in FIGURE 2 taken along the line 3 3.

While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplilication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring first to FIGURE 1 there is shown an air compressor system including an air compressor 10 connected by a line 11 to a container 12. The compressor 10 supplies air under pressure to the container 12 through the line 11 whenever the compressor is operated and a check valve 14 prevents air in the container 12 from returning through the line 11 to the compressor whenever the pressure in the line 11 becomes less than that in the container 12. An embodiment of the present invention is connected to the container 12 by an air line 16 to the air line 11 by a vent line 17, and electrically to a source of electrical current (not shown) by the electrical leads 1S and to the compressor by the electrical leads 19. As will presently be described in detail, the embodiment in the invention senses the pressure of the air in the container l2 via the line 16, vents the line 11 via the line 17 and electrically controls the compressor 1G by having a switching means between lines 18 and 19.

Referring now to FIGURES 2 and 3, a pressure responsive actuator generally indicated at 2%) is attached to a U-shaped frame 21 by a set of bolts 22. The pressure responsive actuator is composed of a iiexible diaphragm 23 and an air line connector 24 secured between the frame 21 and a venting valve support member 25 and a thrust member 27 which is mounted against the flexible diaphragm 23 and passes through an aperture 28 in the frame 2l. The air line 16 shown in FIGURE l, is threaded into an internal threaded portion of the connector 24 to provide an air tight connection between the container 12 and the pressure responsive operator 29. Thus pressure in the container 12 tends to force the diaphragm 23 and the thrust element 27 upward. A cover Z9 lits around the frame 21 to form an enclosure.

The upward movement of the thrust element 27 is resisted by a primary element in the form of an arm 3Q which is pivotally mounted at one end to an upturned portion 31 of the frame 21. A spring 32 under compression bears against the other end of the arm 30 and is secured to the frame 21 by a bolt 33, a cap 34 and a nut 35 in order to urge the arm 30 downwardly. The position of the arm 3G is determined by the relative air pressure acting on the diaphragm 23 and the spring pressure from the spring 32 which may be adjusted by changing the position of the nut 35.

A control in the form of a venting valve 4), having a valve seat 41, a ball fitting said seat to act as a valve, a valve stern 43 forcing said ball off the seat and a spring 44 tending to maintain the ball 42 on the seat 41, is secured to the housing venting valve support member 25 by a nut 45. A secondary element in the form of an arm constructed of resilient material 46 has one end pivotally mounted to the arm 30 as generally indicated at 47 and the other end secured to the valve stem 43 by a pair of nuts S8 threaded onto the stem 43. In the views of the embodiment of the invention shown in FIGURES 2 and 3, the arms 36 and 45 are free to rotate about their pivot points independently of each other.

A mechanical device consisting of an element 56 pivotally mounted to the arm 46 by a shaft 51 is provided to engage a projection 52 of the arm 30 at a notch portion 53 under the influence of a spring 54. A bolt 55 is threaded into an aperture 56 in the frame 21 to form an adjustable abutment to engage a portion 57 of the element 50 as the arm 46 moves downward. A locking nut 53 secures the bolt in a desired position.

A positive action switch generally indicated at 60 has a housing member 61 secured to the U-shaped frame 2l.. The portion of the switch visible in FIGURE 2 shows one pair of switching contacts of which there are two mounted parallel within the housing 61, the second set of contacts being directly behind the ones shown in FIGURE 2. The switch consists of an arm `62 pivotally mounted at 63 to the housing 61, a spring 64 urging the arm 62 against the thrust member 27, an arm 65 pivotally mounted to the housing member 61 at 66 and limited in its downward movement by the head 69 of a bolt 70 threaded into the housing member 61, an arm 71 of flexible metal secured at one end to the mounting post 72 and at the other end to the connecting member 73 which is mounted On the arm 65', a set of electrical contacts composed of a contact 74 on the arm 71 and a contact 75 on a terminal post 76, and a resilient member 77 causing the arm 65 to move in the opposite direction to the arm 62. The switch as illustrated is a conventional type positive action switch having its contacts connected between the lines 18 and 19 to control the operation of the compressor 10 and does not in itself form a part of the present invention.

The operation of the embodiment illustrated in FIG- URES il through 3 will now be described in greater detail. Let it be initially .assumed that the air pressure in the container 12l has dropped to such a low pressure that the elements are in the positions illustrated in FIGURES 2 and 3, with the electrical contacts 74 and 76 and the corresponding contacts (not shown) closing the electrical circuit between the iwires 18 and 19 to start the compressor l). As the compressor operates it gradually raises the pressure in the container 12 which acts on the diaphragm 23 to force the thrust element Z7 upwardly. As the thrust element moves upwardly it carries the arm 30 with it. The upward movement of the arm Sil moves the projection SZ upward allowing the notch portion 53 of the element Sei to rotate against it under the influence of the spring S4. The upward movement of the thrust element 27 will then reach `a point at which the arm 62 has moved sufficiently upward to cause the arm 65 to snap downward under the inuence of the resilient member 77 and disengage the contacts 74 and 76 and the corresponding contacts (not shown) to stop the compressor. The check valve 14 prevents the pressure in the container 12 from backing up into either the compressor 12 or the line 17.

During the above described steps, the valve 40l which is connected to the vent line 17 has remained closed under the iniiuence of the spring 44. As the air pressure in the container 12 gradually drops the thrust element will allow the arm 3i? to move downward under the iniluence of the spring 32. Since the notch 53 of the element SQ is engaging the projection 52 the arm 46 and the valve stem 43 will be forced downward opening the valve 44 by unseating the ball 42 from the valve seat 41, thus allowing the release of air pressure in the lines 17 and 11 to the outside atmosphere. As the downward movement of the arm `i6 is continued the portion 57 of the element 50 will engage the bolt 55 to rotate the element 50 clockwise about the shaft 51. When the element Si? has rotated suciently, the notch 53 disengages from the projection 52 allowing the valve 4l) to close under the inlluence of the spring 44 since the arm 46 is now free to move upwardly independent of the arm Ztl. As the pressure of the container 12 continues to decrease the thrust element '27 ,allows the arm 62 to move downwardly to a point -at which the resilient member 77 snaps the arm 65 up against the abutment 67 re-engaging the contacts to again start the compressor 10.

It may be readily recognized by those skilled in the art that the adjustments required following an installation of an embodiment of the inventions are relatively simple and may be carried out by unskilled personnel. The pressure at which the compressor is stopped is controlled by the setting of the nut 35 which determines the spring force against the arm 3i). The pressure at which the compressor is started is controlled by the setting of the bolt head 69. The pressure at which the venting valve 40 will open to vent the line 11 through the line 17 is controlled by the position of the nuts 48 on the valve stem 43, and the setting of the bolt v5S determines the pressure at which the venting valve 40 is closed. Thus four simple mechanical adjustments determine the two d pressures for operation of a compressor and the two pressures for operation of its compressor unloader.

I claim:

l. ln a control device, the combination of a pressure responsive actuator, a primary element, means for positioning said primary element in accordance with the position of said actuator whereby said primary element is moved in one direction on increasing pressure and in another direction on decreasing pressure, a secondary element movable to operate a control, and a mechanical means connecting said primary element and said secondary element to move said secondary element for operating said control during a portion of the movement of said primary element in one direction, said control being operated only by movement of said primary element in said one direction.

2. In a control device, the combination of a pressure responsive actuator, a primary element moved by said actuator in one direction on increasing pressure and in another direction on decreasing pressure, a secondary element movable to operate a control, and a mechanical device connecting said primary element and said secondary element to move said secondary element for operating said control during a predetermined range of pressure decrease, said control being operative only during `a decrease in pressure.

3. A control for a compressor comprising a pressure responsive actuator, a primary arm pivotally mounted and maintained in Contact with said actuator, said actuator moving in one direction on increasing pressure and in the opposite direction on decreasing pressure, a control means having an operator, a secondary arm pivoted at one end and connected to said operator, an element pivotally mounted on said secondary arm to allow said primary arm to move independently of said secondary arm during a change in pressure in one direction yand to engage a portion of said primary arm during a change in pressure in the opposite direction whereby said operator is moved by the movement of said secondary arm with said primary arm, and an abutment engaging -a portion of said element at a point in the movement of said secondary arm with said primary arm to disengage said element from said primary arm.

'4. A control for `a compressor comprising a pressure responsive actuator, a primary arm pivoted at one point ,and maintained in contact with said actuator at another point, said actuator moving in one direction on increasing pressure and in the opposite direction on decreasing pressure, a valve having a stem, means biasing said valve to a closed position, a secondary arm pivoted at one point and connected to said valve stem at another point to open and close said valve, an element pivotally mounted on said secondary arm, means acting between said element and said secondary arm to maintain said' element in contact with said primary arm to allow said prirnary arm to move independently of said secondary arm during an increase in pressure and to cause said element to engage a portion of said primary arm during a decrease in pressure whereby said valve is opened by the movement of said secondary arm with said primary arm, and an abutment engaging a portion of said element at Ia point in the movement of said secondary arm to disengage said element from said primary arm whereby said valve is allowed to return to its closed position.

5. A control for a compressor comprising a pressure responsive actuator, a primary arm pivoted at one end and in contact with said actuator, a spring biasing said arm to maintain it in Contact with said actuator, said actuator moving in one direction on increasing pressure and in the opposite direction on decreasing pressure, a valve having a stem, means biasing said valve to a closed position, a secondary arm pivoted at one end and connected to said valve stem to open and close said valve, resilient means acting to bias said valve to its closed posi- 5011, an element pivotaly mounted on said secondary 5 arm, a spring acting between said element and said secment of said secondary rarrn to pivot said element for Cndary arm o maintain said element in contac with said disengagement from said primary arm whereby said valve primary arm to allow said primary arm to move ndeis allowed to return to its closed position. pendently of said secondary arm during an increase in pressure and to cause said element to engage a portion 5 Refeems @mi l the file 0f this Patent of said primary arm during a. decrease in pressure where- UNITED STATES PATENTS by said valve is opened by tne movement of said secondo ary arm with said primary arm, and an abutment engaging a porion of said element at a point in the move- 

2. IN A CONTROL DEVICE, THE COMBINATION OF A PRESSURE RESPONSIVE ACTUATOR, A PRIMARY ELEMENT MOVED BY SAID ACTUATOR IN ONE DIRECTION ON INCREASING PRESSURE AND IN ANOTHER DIRECTION ON DECREASING PRESSURE, A SECONDARY ELEMENT MOVABLE TO OPERATE A CONTROL, AND A MECHANICAL DEVICE CONNECTING SAID PRIMARY ELEMENT AND SAID SECONDARY ELEMENT TO MOVE SAID SECONDARY ELEMENT FOR OPERATING SAID CONTROL DURING A PREDETERMINED RANGE OF PRESSURE DECREASE, SAID CONTROL BEING OPERATIVE ONLY DURING A DECREASE IN PRESSURE. 